Chemical Names and Formulas

MoleculesA molecule is the smallest electrically neutral unit of a

substance that still has the properties of the substance.

1. Monatomic - consist as a single atom (Ex: Noble gases)

2. Diatomic molecule -7 exist in nature “BrINCl HOF”

3. Triatomic molecule ( Ex: O3 - ozone)

He

(means 2) atomsBr2 I2 N2 Cl2 H2 O2 F2

Chemical Formula: shows the kinds and numbers of atoms in the smallest representative unit of the substance (formula unit)

REMEMBER!!!!H – Element symbol always begins with a capital letter

Na – If symbol has two letters, the second letter is always lowercase

H2O H2O2

What’s the difference between these two formulas?When you change the subscripts the formula no longer represents that compound.

Chemical FormulasHow to read formulas:

H2O = 2 hydrogen atoms

1 oxygen atom

Ca(OH)2 – Number outside the parenthesis distributes to inside the parenthesis

1 calcium atom2 oxygen atoms2 hydrogen atoms

Explain the following:

MgCl2 – What elements are present? How many? Mg - Cl -

Pb(NO3)2 – What elements are present? How many?

Pb - N - O -

1

2

1

2

6

Ionic Charges of Representative Elements

1A 2A 3A 4A 5A 6A 7A 8A

Li+

Na+

K+

Rb+

Cs+

Be2+

Mg 2+

Ca 2+

Sr 2+

Ba 2+

Al3+

N3-

P3-

As3-

O2-

S2-

Se2-

F-

Cl-

Br-

I-

Oxidation Numbers – how many electrons an atom would gain or lose to follow the octet rule

(also called its charges)

+1

+2 +3 -1-2-3

Charges of Transition Metals

These transition metals have more than one charge:

Cr2+ or 3+ Cu+ or 2+

Mn2+ or 3+ Sn2+ or 4+

Fe2+ or 3+ Pb2+ or 4+

Co2+ or 3+ Ni2+ or 3 +

Hg1+ or 2+ Au1+ or 3 +

Sc2+ or 3+ Hg1+ or 2 +

I. Writing Formulas for Binary Ionic Compounds

Rules:1. Write symbol and charge for both

cation and anion.

2. Crisscross charges, drop the charge and write as subscripts.

3. CHECK!! The formula must be in the lowest possible ratio.

The cation is always written first!

Example Problems

Write formulas for these compounds:

calcium iodide

Ca I+2

-

CaI2

21

O -2

Tin (IV) oxide

Sn+4

Sn2O4 SnO2

42

Aluminum sulfide

Al S

Al2S3

+3

-232

White Board Practice

Be O

BeO

+2

-2Beryllium Oxide

2 2

Be2O2

II. Naming Binary Ionic Compounds

1.) Use the name of the cation. ****Use Roman Numerals if Transition Metal.

2.) Name the anion and change ending to -ide.

SnS2

Naming Binary Ionic Compounds

Use Roman Numerals

Tin(IV)

Find SnWhere is it located?-

2

Sulfide

+4

+2

-1

B.) CuBr2

WHITE BOARD practice problemsA.) KCl

C.) AlF3

D.) MgO

E.) MnI2

Al+3 P-3

1.) K+ S-

2

White Board Practice

2.) Al+3 I-

3.) Ag+ O-2

4.) Ni+2 O-2

5.) Pb+4 O-2

Polyatomic Ions• Tightly bound groups of atoms that behave

as a unit and carry a charge.

Ammonium NH4

+Cyanide

CN-

Sulfite SO3

2-

Examples:

III. Writing Formulas for Ternary Ionic Compounds

A. Contain a polyatomic ion

B. Same rules as for binary ionic compounds.

One addition – Use parenthesis if there is more than one polyatomic ion

Ex:

Calcium Hydroxide

Ca2+ OH-

CaOH2

Ca(OH)2

• Boron acetate

B3+ C2H3O2-1

• Magnesium Dichromate

Mg+2 Cr2O7-2

White Board Practice Problems Write formulas for the following

ternary ionic compounds:a. Calcium Carbonate

b. Barium Nitrite

c. Potassium Sulfate

d. Magnesium Phosphate

IV. Naming Ternary Ionic Compounds

• Same rules as for naming binary ionic compounds:–Name the cation

***Use a Roman numeral if necessary

–Name the anion (change ending to –ide) Polyatomic ions will stay the same!!

White Board Practice Problems:• Name the following ternary ionic

compounds:a. NaCN

b. NH4ClO

c. Li2SO3

d. CaC2O4

e. Al(OH)3

f. Sn3(PO4)2

Ionic Compounds- Polyatomic IonsLeft Side of Spiral

Cl OH SO4 PO4 NO3

Zn+2

NH4

K

Ca

Fe+3

-1-1 -2 -3-1

+

+

+2

V. Rules for Naming Covalent Compounds

1. Prefixes are used to show how many atoms of each element are present in the compound

Prefixes used for Naming Binary Covalent Compounds

2. Second element is written with an –ide ending.

***All binary compounds, both ionic and covalent end in –ide.

3. The vowel at the end of the prefix is dropped when the name of the element begins with the same vowel.

Ex: monoxide, not monooxide

Rules for Naming Covalent Compounds

4. Mono is omitted if there is just a single atom on the first element in the name.

Ex: CO2

carbon dioxide not monocarbon dioxide

Rules for Naming Covalent Compounds

Naming Binary Covalent Compounds

1.) CO

2.) SO2

3.) N2O

4.) CCl45.) N2O5

6.) NO4

7.) OF2

Writing Formulas for Binary Covalent Compounds

Write the formulas for the following compounds.

1. carbon monochloride

2. nonacarbon tetrachloride

3. heptabromine dioxide

4. phosphorus trichloride

5. octanitrogen pentafluoride

Ionic vs. CovalentAre the following compounds ionic or covalent?

b. Sodium chloridec. CuSO4d. CO

e. Lithium hydroxide

f. dinitrogen tetraoxide g. FeS

h. Cobalt (III) chloridei. H2S

j. PF3

a. H2O

Naming Acids

• HCl hydrochloric acid

• H2SO4 sulfuric acid

• HNO3 nitric acid

• HC2H3O2 acetic acid

• H3PO4 phosphoric acid

• H2CO3 carbonic acid

ECHS Relay Challenge1.) How many atoms of fluorine are present in CF4? 2.) How many atoms of carbon are present in CF4?3.) What is the formula for carbon monoxide?4.)What is the formula for lithium chloride?5.) What is the formula for the compound formed by iron (II) and carbonate ions?6.) What is the formula for aluminum hydroxide?7.) What is the formula for lead (IV) oxide?8.) What is the formula for magnesium nitrate?9.) What is the name of the compound: NH3? CCl4?10.) What is the cation in iron (II) oxide?11.) What is the name of the compound N2O2? H2O2?12.) What is the formula for sulfur trioxide?13.) What is the formula for dinitrogen tetrafluroide?14. )What prefix is used to represent ten?15.) How do you know a compound is covalent when looking at the chemical formula?16.) Using the ion pairs listed, write the correct chemical formula that the ions would form:

a. Cr+3 I- = b. Cu+2 O-2 = c. Li+ S-2 =17.) What is the oxidation number for iron (II) in iron (II) oxide?18. Write the names for the compound FeO and Fe2O3. Justify why the names you wrote are

correct.19.) What are the seven diatomic elements?20.) What is the name of the compound Si2Br6?21.) Write the formula for diboron hexahydride.22.) Write the formula for oxygen gas.